Upload
truonghanh
View
213
Download
0
Embed Size (px)
Citation preview
FABRICATION OF 316L STAINLESS STEEL (SS316L) FOAM VIA POWDER
COMPACTION METHOD
ZULAIKHA BTE ABDULLAH
A thesis as a partial fulfillment of the requirements for the award of the
Master of Mechanical Engineering
Faculty of Mechanical and Manufacturing Engineering
Universiti Tun Hussein Onn Malaysia
JUNE 2015
v
ABSTRACT
Metal foam is the cellular structures that made from metal and have pores in their
structures. Metal foam also known as the porous metals, which express that the
structure has a large volume of porosities with the value of up to 0.98 or 0.99. Porous
316L stainless steel was fabricated by powder metallurgy route with the composition
of the SS316L metal powder as metallic material, polyethylene glycol (PEG) and
Carbamide as the space holder with the composition of 95, 90, 85, 80, and 75 of
weight percent (wt. %). The powders were mixed in a ball mill at 60 rpm for 10
minutes and the mixtures were put into the mold for the pressing. The samples were
uniaxially pressed at 3 tons and heat treated by using box furnace at different
sintering temperature which are 870°C, 920°C, and 970°C separately. The suitable
sintering temperature was obtained from the Thermal Gravimetric Analysis (TGA).
There are several tests that have been conducted in order to characterize the physical
properties of metal foam such as density and porosity testing, and the morphological
testing (Scanning Electron Microscopy (SEM)), and Energy Dispersive X-ray
(EDX). From the result, it can be conclude that, the sintering temperature of 920°C
was compatible temperature in order to produce the metal foams which have large
pores. Other than that, the composition of 85 and 75 wt. % is the best compositions in
order to creates the homogenous mixture and allow the formation of large pore
uniformly compared to other compositions which in line with the objective to
produce foams with low density and high porosity which suitable for implant
applications. The average pore size was within range 38.555µm to 54.498 µm which
can be classified as micro pores.
vi
ABSTRAK
Logam berbusa adalah struktur sel yang diperbuat daripada logam dan mengandungi
liang-liang di dalam strukturnya. Logam berbusa yang juga dikenali sebagai logam
berliang yang mempunyai sejumlah besar keporosan pada strukturnya dengan nilai
sehingga 0.98 atau 0.99. Struktur berliang 316L keluli tahan karat telah difabrikasi
dengan kaedah metalurgi serbuk dengan komposisi serbuk logam SS316L sebagai
bahan logam, Polyethylene Glycol (PEG) sebagai penguat dan Baja Urea sebagai
pemegang ruang dengan komposisi bahan 95, 90, 85, 80, dan 75 peratus berat (wt.
%). Kesemua serbuk dicampur dan diadun menggunakan pengisar bebola pada
kelajuan 60 rpm dalam masa 10 minit dan campuran dimasukkan ke acuan untuk ke
proses penekanan. Sampel dipadatkan dengan tekanan 3 tan dan di sinter
menggunakan relau kotak pada suhu yang berbeza iaitu 870°C, 920°C, dan 970°C
secara berasingan. Suhu sinter yang sesuai diperolehi daripada Analisis Gravimetrik
Haba (TGA). Terdapat beberapa ujikaji dijalankan untuk mencirikan sifat fizikal
logam berbusa seperti ujikaji ketumpatan dan keliangan, ujikaji morfologi dengan
menggunakan Pengimbas Mikroskopi Elektron (SEM) dan Tenaga Serakan Sinar-X.
Daripada keputusan, dapat dirumuskan suhu sintering 920°C adalah paling sesuai
untuk digunakan untuk menghasilkan sampel dengan saiz liang yang besar. Selain itu
komposisi 85 dan 75 wt. % adalah komposisi terbaik, di mana komposisi ini
menghasilkan campuran yang homogen yang membenarkan pembentukan liang yang
besar secara seragam di mana selaras dengan objektif asal kajian untuk menghasilkan
logam berbusa yang mempunyai ketumpatan yang rendah dan keliangan yang tinggi
di mana sesuai untuk aplikasi implan. Purata saiz liang adalah dalam julat 38.555µm
hingga 54.498µm dan boleh diklasifikasikan sebagai liang mikro.
vii
TABLE OF CONTENT
Page
TITLE i
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii-ix
LIST OF FIGURES x-xii
LIST OF TABLES xiii
CHAPTER 1 INTRODUCTION
1.1 Background of Study 1
1.2 Problem Statement 3
1.3 Objective of Study 3
1.4 Scopes of Study 3
CHAPTER 2 LITERATURE REVIEW
2.1 Introduction 4
2.1.1 Metal Foams 5
viii
2.2 Metallic Material 6
2.2.1 Stainless Steel 8
2.2.2 Designation of Stainless Steel 11
2.2.3 Classification of Stainless Steel 13
2.3 Binder 15
2.3.1 Polyethylene Glycol (PEG) 16
2.4 Space Holder 18
2.4.1 Carbamide (Urea) 19
2.5 Fabrication Techniques 21
2.5.1 Metal Foam Fabrication Techniques 21
2.5.2 Fabrication Foams using Slurry Foaming Techniques 23
2.5.3 Fabrication Foams using Powder Metallurgy 25
Techniques
2.5.3.1 Powder Mixing 27
2.5.3.2 Compaction Process 28
2.5.3.3 Sintering Process 30
2.6 Research Parameters 32
2.6.1 Effect of Composition 32
2.6.2 Effect of Sintering Temperature 33
ix
CHAPTER 3 METHODOLOGY
3.1 Introduction 34
3.1.1 Flow Chart 35
3.2 Main Material 36
3.2.1 Raw Material 36
3.2.2 Polyethylene Glycol (PEG) 38
3.2.3 Carbamide (Urea) 39
3.3 Meshing Process of Space Holder Material 40
3.3.1 Crushing Process 40
3.3.2 Sieving Process 41
3.4 Powder Metallurgy Techniques 42
3.4.1 Mixing Process 42
3.4.2 Compaction Process 43
3.4.3 Sintering Process 45
3.5 Testing Method 48
3.5.1 Thermal Gravimetric Analysis (TGA) 48
3.5.2 Density and Porosity Test 49
3.5.3 Scanning Electron Microscopy (SEM) 51
3.5.4 Energy Diffraction X-ray (EDX) 52
x
CHAPTER 4 RESULT AND DISCUSSION
4.1 Introduction 54
4.2 Thermal Gravimetric Analysis (TGA) 54
4.2.1 Thermal Gravimetric Analysis 55
for Stainless Steel (SS316L)
4.2.2 Thermal Gravimetric Analysis 56
(TGA) for Carbamide (Urea)
4.2.3 Analysis of Thermal Gravimetric Analysis 58
(TGA) for polyethylene glycol (PEG)
4.3 Analysis of Density and Porosity Test 59
4.4 Scanning Electron Microscopy Analysis (SEM) 63
4.5 Energy Diffraction X-ray Analysis (EDX) 77
CHAPTER 5 CONCLUSION AND RECOMMENDATION
5.1 Conclusion 82
5.2 Recommendation 84
REFERENCES 86
APPENDIXES
xiii
LIST OF TABLES
Tables Page
2.1 Standard composition of 316L Stainless Steel 10
2.2 The sintering temperature and time of sintering for different metal 31
Powders
3.1 Material designation in accordance with Metal Powder Industries 37
Federation (MPIF) standard 35
3.2 Composition of SS316L Pure, SS316L with PEG and Carbamide 42
3.3 Labeling of Samples SS316L Pure, SS316L with PEG and Carbamide 43
3.4 Summary of maximum service temperature on Air for Stainless Steel 47
4.1 Result for density test of SS316L foams at sintering temperature of 59
870°C, 920°C, and 970°C
4.2 The average result for porosity test of SS316L foams at 61
sintering temperatures of 870°C, 920°C, and 970°C
4.3 Average of Pore Size for the SS316L Foams with Different Composition 71
4.4 Element Mass Percentage Presence at Samples for EDX Analysis at 77
Sintering Temperature of 870°C
4.5 Element Mass Percentage Presence at Samples for EDX Analysis at 78
Sintering Temperature of 920°C
4.6 Element Mass Percentage Presence at Samples for EDX Analysis at 79
Sintering Temperature of 970°C
4.7 Element mass percentage presence at Samples for EDX analyses of 80
the structure that represent the corrosion are on the sample with
composition of 75 wt. % at sintering temperature of 870°C
1
CHAPTER 1
INTRODUCTION
1.1 Background of Study
At present, high requirement of lightweight constituent make metal foams extremely
attractive as an industrial technology for biomedical application which is demanding
on weight reduction (Gauthier, 2008). The physicality of metal foam is high porosity
make metal foams very lightweight. Basically, metal foams are artificial porous
medium that has solid matrix structure of metal consist of empty or fluid-filled voids.
Metal foams have been characterized into two types which are open-cell and closed-
cell. The foams is called open-cell when the voids are connected via open pores, but
when the foams are separated by the solid walls and not connected via open channel
are described as closed-cell (Dukhan, 2013).
In order to achieve the metal foams which suitable in orthopedic application
and have good properties such as low density, high strength-to-weight ratio, excellent
mechanical properties, biocompatibility and corrosion resistance, the suitable
materials have to choose carefully. Metals are the most suitable material to fabricate
the metals foam proportionate to the ceramic and polymer. Even though the ceramic
material have excellent corrosion resistance but ceramic cannot being employed as
load bearing implants due to their brittle properties, whereas polymeric systems
cannot sustain the mechanical forces present in joint replacement surgery (Ryan,
Pandit & Apatsidis, 2006). There are various types of metal that have been used as
main materials to fabricated metal foams includes titanium, titanium alloys, nickel,
aluminum, magnesium, and stainless steel(Rosip et al., 2013).
2
Since early 1960s, Stainless steel widely used in orthopedic application such as
fabrication of femoral stems, balls and acetabular cups, fabrication of knee and
femoral components and tibial trays because of its biocompatibility and inexpensive
(Davis, 2003). Porous Stainless steel is compatible to use as a coating on Stainless
steel implants. The methods that use to fabricate these coating are by sintering beads
or thermal spray techniques. The oxides that formed on the surfaces of stainless steel
is more stable than the oxides formed if using titanium and titanium alloys and leads
to the crevice corrosion and degradation of the implants. Because of that, Stainless
steel is choosing to replace other materials over the year. Stainless steel has been
approved in terms of mechanical properties and clinical trials by the US Food and
Drug Administration (FDA). Its mechanical properties are often used as bench mark
criteria to evaluate other alloys for stent applications (Chen et al., 2014).
There are large varieties of fabrication techniques for metal foams or similar
porous structures but usually favorable technique is liquid phase or powder
metallurgy process. By using compaction method, metal powders are mixed with
foaming agent and then compacted by using hot pressing, cold pressing, hot
extrusion, or co-extrusion. The final product of the compaction process is a dense
foamable material that can be worked into sheets and profiles (Banhart &
Baumeister, 1998) Slurry method are commonly used to produce metal foams by
providing metal powder, blowing agent and a binder that mix together and the
mixture poured into mould and left to the elevated temperature until melting
temperature(Rosip et al., 2013). Casting process also has been used to produce metal
foams around inorganic hollow spheres with a liquid melt or using open porosity
polymer foams as starting points.
This research is to fabricate the 316L Stainless Steel (SS316L) foam prepared
by Compaction technique and to study and characterize the properties of SS316L
foam after sintering process. The SS316L have used as a raw material and
Polyethylene glycol (PEG) and Carbamide are used as a binder and space holder
respectively. The material will be mixed by using ball milling machine to get the
homogenous mixture. After that the compaction process will be held by using
conventional axial pressing. This process is known as powder metallurgy technique.
The Properties Characterization will be measured by doing density and porosity test,
Thermal Gravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), and
Energy Diffraction X-ray (EDX).
3
1.2 Problem Statement
The major challenges that need to focused while producing metal foam is the
mismatch of the properties between bones and the metallic material. Due to this
mechanical mismatch, bone is insufficiently loaded and become stress shielded,
which eventually leads to bone resorption (Ryan et al., 2006).
Thus, there are factors need to be considered includes the interconnecting
pores that suitable with bone, the pores of the implants same with the pores of bone,
the shape and the density of implants is same with the shape and density of bones.
1.3 Objectives
The objectives of this research are:
i) To fabricate the 316L Stainless Steel (SS316L) as metallic cell
prepared by Compaction technique.
ii) To characterize the properties of fabricated SS316L foam after
sintering process.
1.4 Scope of Study
The scope of this research includes:
i) The percentage of the composition for the SS316L powder are 95, 90,
85, 80 and 75 of weight percent (wt. %) respectively, for the
Polyethylene glycol is 1 of weight percent (wt. %) and balance is for
the Carbamide composition.
ii) The sintering temperatures that have been choosing are 870ᴼC, 920ᴼC,
and 970ᴼC.
iii) The characterization for the properties of metal foam will be study by
conducted the Thermal Gravimetric Analysis (TGA), Density and
porosity test, Scanning Electron Microscopy (SEM), and Energy
Diffraction X-ray (EDX).
4
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
This chapter justify about literature review of the research to gather information and
knowledge of the material that need to be used in this research, the method that have
been used in previously study and the method that has been select in this research.
This section focused on the Stainless Steels and its properties, the binder and space
holder that has been used and the fabrication method that involved.
5
2.1.1 Metal Foam
Basically, metal foam can be described as the cellular structure that made from metal
and have pores in their structures. Metal foam also known as the porous metals,
which express that the structure has a large volume of porosities with the value of up
to 0.98 or 0.99. The high porosity contributes lightweight to the metal foams.
Besides, the terms foamed metal or metallic foam illustrate the fabrication or forming
process of the metal foam.
Metal foams have been characterized into two types of structure which are
open cell and closed cell. The structure of the porous metals influences the
applications of the metal foams. Closed cell foam can be described as the pores is fill
with gas and separated from each other by metal cell walls, have good strength and
usually used in structural application. Open cell foam contain a continuous network
of metallic struts and the enclosed pores in each strut frame are connected, the
strength are weaker than the closed cell and are mainly used in functional
applications where the continuous nature of the porosity is exploited (Kennedy,
2012). Figure 2.1 show the example of the microstructure of closed cell foam and
open cell foam for metal foams.
Figure 2.1: Microstucture of (left) a closed cell foam and (right) an open cell
foam (Kennedy, 2012)
6
There are other application of metal foams such as energy absorber, heat
exchangers, mechanical damping and in filters system. Nowadays, metal foams has
been use in biomedical application as bone implants. Metal foams have excellent
potential for implant application due to its low density and good combination of
properties because of the reduced stiffness mismatches. Other than that, it is
important to make sure the bone ingrowth which possible by metal foams and greatly
improve the bone implant interface and may allow for efficient soft tissue attachment
supplementing the stability of the implant by biological fixatation (Mariotto et al.,
2011).
2.2 Metallic Material
The excellent of electrical and thermal conductivity and mechanical properties make
metal used as biomaterials which suitable used as biomedical materials. Biomaterial
can be expressed as any material used to make devices to replace a part or a function
of body in a safe, reliable, economic, and physiologically acceptable manner (Park &
Lakes, 2007). Metals offer excellent strength and resistance to fracture, which
suitable for the medical application that requiring load bearing.
There are number of metallic material that good biocompatibility which are
not cause serious toxic reaction in human body such as Stainless Steels, Cobalt
Alloys, Titanium Alloys and noble metals. These metals are suitable for the
structural application in the body such for implants for hip, knee, ankle, shoulder,
wrist, finger, or toe joints. These metals have the ability to bear significant loads,
withstands fatigue loading, and undergo plastic deformation prior to failure, made
these metals are popular chosen as material for the implant application (Shi, 2006).
Some metals have high corrosion resistances which made its suitable used as
passive substitutes for fracture healing aids as bone plates and screws, spinal fixation
devices, and dental implants. Corrosion can be defined as the unwanted chemical
reaction of a metal with its environment, resulting in its continued degradation to
oxides, hydroxides, or other compound. It is important to choose metallic materials
which have high corrosion resistance due to its biocompatibility in human body.
7
Other than that, metallic material play active roles in devices such as vascular stents,
catheter guides wires, orthodontic arch wires, and cochlea implants (Park & Lakes,
2007). Figure 2.2 show the typical implant applications for orthopedic purposes.
During the twentieth century, the first metallic material was successfully used
in orthopedic applications were Stainless Steels and Cobalt-Chrome Based Alloys
(Navarro et al., 2008). The Stainless Steels and Cobalt-Chrome Based Alloys have
high corrosion resistance based on the presence of Chromium in their properties
make it has the ability to render the alloys passive. In this research, the metallic
material that has been used is Stainless Steels which will be explained later.
Figure 2.2: The typical implant applications for orthopedic purposes (Davis,
2003)
8
2.2.1 Stainless Steels
Stainless Steels are widely used in modern metallurgy. Historically, Stainless Steel
was discovered in early 18th and 19th centuries; when the identification of Chromium
as an element was begin. Harry Brearley (1871-1940) who first produced the first
commercial cast of martensitic Stainless Steel, which used for cutlery area (Cobb,
2010).
Different from other alloy systems that has widely used such as Carbon
Steels, Alloy Steels, and Aluminum Alloys, that are relatively dilute solution of
several element in the parent matrix. Stainless Steel is one of alloys system that it is
not a dilute solution. There are several percent of alloying element that contained in
Alloys steels includes Carbon, Manganese, Nickel, Molybdenum, Chromium, and
Silicon, Impurities Sulfur, Oxygen, And Phosphorus. Typically, Alloy Steels contain
very small of amounts of Titanium, Niobium and Aluminum. In contrast, in about
11% of Chromium that contain alone in Stainless Steel (McGuire, 2008). Usually,
the shape of Stainless Steels particles is irregular. Figure 2.3 show the basic shape of
metal powder (Kalpakjian & Schimid, 2006).
Figure 2.3: Basic shape of Metal powder (Kalpakjian & Schimid, 2006)
9
Basically, Stainless Steel is Iron-Base Alloys that contain a minimum of
approximately 11% of Chromium (Cr), amount that needed to prevent the formation
of rust in unpolluted atmosphere. There are few Stainless Steels contain more than
30% Cr or less than 50% Ferum (Fe). They fulfill the Stainless Steel characteristics
condition by the formation of an invisible and adherent Chromium rich oxide surface
film. The process is happen when the oxide forms and heals itself in the presence of
oxygen (Davis, 1994).
There is development of Stainless Steels that used in implant application. The
first Stainless Steel that has been recorded that utilize as implant fabrication was the
18-8 type which is stronger and more resistance to corrosion than the Vanadium
Steel. There are some improvement has been done to Stainless Steel by attached a
small percentage of Molybdenum to improve the corrosion resistance in Chloride
solution which next the Stainless Steel has known as type 316 Stainless Steels.
During 1950s, they upgrade the Stainless Steel by reducing the amount of Carbon
content from 0.08 to a maximum amount of 0.03% to increase corrosion resistance
and minimize the sensitization and become as type 316L Stainless Steels. The
Chromium content also function as the reduction of Carbon content in which to
impart corrosion resistance in Stainless Steel which the concentration of Chromium
is 11% (Wong & Bronzino, 2007).
The type of Stainless Steels that most widely used for implant fabrication is
the austenitic Stainless Steels which is type 316 and 316L. These groups of steel are
nonmagnetic and have better corrosion resistance than others because the content of
Molybdenum that enhances the resistance while attach in the salt water. The
American Society of Testing and Material (ASTM) recommend type 316L rather
than type 316for fabrication for implant. The standard composition of 316L Stainless
Steel that follows American Society for Testing and Materials is show in Table 2.1
(Wong & Bronzino, 2007).
10
Table 2.1: Standard composition of 316L Stainless Steel (Wong & Bronzino,
2007)
Element Composition (%)
Carbon 0.03 max
Manganese 2.00 max
Phosphorus 0.03 max
Sulfur 0.03 max
Silicon 0.75 max
Chromium 17.00-20.00
Nickel 12.00-14.00
Molybdenum 2.00-4.00
Ferum Balance
Mariotto et al., (2011) in the study of fabrication metal foam for biomedical
application have used Stainless Steel type 316L as main material. Ammonium
Carbonate and Ammonium Bicarbonate is chosen as foaming agents that will mix
with the Steel powder. The technique that has been applied to fabricate the metal
foam is by using powder metallurgy techniques and the metal foam vacuum heat
treated in 2 stages, the first stage at 200°C for 5 hours to decompose the carbonate
and the second stage at 1150°C for 2 hours to sinter the steel. From the research, the
density of the metal foam is in about 0.3 g.cm? ? and 0.5g.cm? ? for Ammonium
Carbonate and Ammonium Bicarbonate foaming agents respectively. The
microstructure of the metal foam is heterogeneous pore structures, composed by
irregular and isolated pores. The result show that the metal foam produced can be
viable in orthopedic implants (Mariotto et al., 2011).
The previous researchers produce of 316L Stainless Steels foam via slurry
method. In the research, the 316L Stainless Steel is chosen as metallic material,
where the Polyethylene Glycol (PEG) and Methylcellulose (CMC) were used as
binder. The result shown that, the SS316L metal foams had been successfully
produced by using slurry method. The microstructure observation show that the
metal foams had closed pore than open pore and the powder particles did not well
growth to combine each other after sintering process. At the end of the research, the
suitable composition of SS316L for metal foams fabrication is gained with the
suitable sintering temperature which resulted better strength of metal foams (Rosip et
11
al., 2013). Gauthier (2008) in his study of structure and properties of open-cell 316L
Stainless Steels foams produced by a powder metallurgy-based process used type
316L Stainless Steel as main material, a polymeric binder, and chemical foaming
agent. All the material was dry mixed, then the mixture was molded and heat
treatment is applied to the metal foam. From the result of the investigation, the 316L
Stainless Steels foams was produced and the heterogeneous foams feature a mix of
open and closed pores depending on processing conditions. The mechanical
properties that get from the test show that the value is following the scaling for metal
foams and was related to foam density (Gauthier, 2008).
In this research, the 316L Stainless Steels is choosing as main material. The
characteristic of the 316L Stainless Steel will be elaborate later in the next topic.
2.2.2 Designation of Stainless Steels
The designation of Stainless Steels can be divided into three different designation
systems in principle which are the designation of wrought Stainless Steels, cast
Stainless Steels and P/M Stainless Steels. Basically, in United States the American
Iron and Steel Institute (AISI) numbering system and the Unified Numbering System
(UNS), are design the wrought grades of Stainless Steels. Other major industrial have
also been established other designation system of Stainless Steels but it also similar
to the AISI. Basically for wrought Stainless Steels, the UNS designation consist of
the letter “S”, follow by a five-digit number whereas for those alloys that have an
AISI designation, the first three digit of the UNS designation usually correspond to
an AISI number. The UNS designation consists of the letter “N” followed by a five-
digit number when Stainless Steels that contain high Nickel content (>25 to 35%)
(Reardon, 2011).
There are institutions which call as High Alloy Product Group of the Steel
Founder’s Society of America, also known as the Alloy Castings Institute (ACI), has
designated standard cast Stainless Steels grades. The composition and properties of
the Stainless Steels similar to the wrought grades, and some cast Stainless Steels are
modified in order to improved cast ability and the higher silicon levels are typically
12
used in cast Stainless Steels for the improvement. The designated of Cast Stainless
Steels as alloys intended primarily for liquid corrosion service (C) or high-
temperature service (H). The nominal Chromium-Nickel type of the alloy denotes by
the second letter of the designation and it will change when the Nickel content
increases. The maximum Carbon content (percentage x100) is represented by the
numeral or numerals following the first two letters. When there are another alloying
element is present, these are indicated by the addition of one or more letter as a
suffix. So that, from the Figure 2.4 it can be described that the designation of CF-8M
refers to an alloy for corrosion-resistant service (C) of the 19Cr-9Ni type, with the
maximum Carbon content 0.08% and containing Molybdenum (M) (Davis, 2000).
Figure 2.4: Chromium and Nickel contents in ACI standard grades of
heat-resistant and corrosion-resistant Stainless Steel castings (Davis, 2000)
The Metal Powder Industries Federation (MPIF) establishing the designation
for P/M products. The popular grades of wrought Stainless Steels have been taking
as mark of derivation of new composition of P/M Stainless Steels. Because of that,
the characteristics of most P/M Stainless Steels are parallel to the wrought Stainless
Steels. The wrought Stainless Steels have a maximum of Carbon content of 0.08% or
higher but there are few selected of wrought Stainless Steels are available in a low
Carbon with maximum Carbon content of 0.03% and these are designated as “L”
grades. For the P/M Stainless Steels, with the exception of the martensitic grades, are
specified to be “L” grades or the low Carbon of the alloys. There are reasons on why
the P/M Stainless Steels need for the low Carbon requirement includes low Carbon
13
content renders the Stainless Steels powder soft and ductile, making it easier to
compact, and it minimize the potential for Chromium Carbide formation or being
sensitive during cooling from the sintering temperature (Davis, 2000).
2.2.3 Classification of Stainless Steels
The classification of Stainless Steels can be divided into five which are
martensitic, ferritic, duplex, and austenitic which based on the characteristic
crystallographic structure of the alloys while the fifth is the precipitation-hardenable
alloys which based on the type of heat treatment used. Figure 2.5 illustrate the
common crystal structure of metal such as body-centered cubic (BCC), face-centered
cubic (FCC), and hexagonal close-packed (HCP) (Shi, 2006).
Figure 2.5: The common crystal structure of Metal such as body-centered cubic
(BCC), face-centered cubic (FCC), and hexagonal close-packed (HCP) (Shi, 2006)
Martensitic Stainless Steel can be described as Fe-Cr-C alloys that possess
body-centered tetragonal crystal structure (martensitic) in the hardened condition.
The properties of martensitic Stainless Steel are ferromagnetic, hardenable by heat
treatments, and generally resistant to corrosion in mild environments. These types of
Stainless Steel have high hardness value make it suitable for dental and surgical
instruments. Basically, ferritic Stainless Steel contain Iron-Chromium Alloys with
14
body-centered cubic (bcc) crystal structures. The applications of these types of
Stainless Steel are solid handles for instruments, guide pins and fastener. Duplex
Stainless Steel is a two phase alloys which have equal proportions of ferrite and
austenite phases in their microstructure and characterize by their low carbon content,
additions of molybdenum, nitrogen, tungsten, and copper. Different from other types
of Stainless Steel that have applications in biomedical, duplex Stainless Steel are
commonly used in the oil and gas, petrochemical, pulp and paper industries. The
precipitation-hardenable (PH) Stainless Steel is the only type of Stainless Steel that
classified by the heat treatment. Basically, these types of Stainless Steel are
Chromium-Nickel grades that can be hardened by an aging treatment which can be
classified into three categories which are austenitic, semi-austenitic and martensitic.
Usually, the precipitation-hardenable (PH) Stainless Steel has applied in medical
such as neurosurgical aneurysm and micro vascular clips and various types of
surgical and dental instruments (Davis, 2003).
In this research, the type of the Stainless Steels that will be used can be
classified as austenitic Stainless steels. Austenitic Stainless steel has largest numbers
of alloys and use. Same with the ferritic Stainless steel, the austenitic Stainless Steel
cannot be hardened by heat treatment. The other properties for the austenitic
Stainless steels are nonmagnetic in the annealed condition and can be hardened only
by the cold working. The application for the austenitic Stainless Steel such dental
impression trays, guide pins, holloware, and hypodermic needles, sterilizer, and other
application that have a complex shape. These type of Stainless Steels also has widely
used for implants (Davis, 2003).
15
2.3 Binder
Binders play an important role in processing of component by using pressing
method. Basically binders can be described as multi-component mixtures of several
Polymers which consist of some additives that add to the primary component include
dispersants, stabilizers, and plasticizers. The function of the binders is to assist in
shaping of the component during the process of fabrication to provide strength to the
shaped component. Binders also hold the metal particles together until the onset of
sintering. The density of a pressing (small pressed part) increases with the use of a
binder plasticizer). The binder’s properties can influence on the metal particles
distribution, shaping process, dimensions of the shaped component, and the final
properties of the sintered component. The binder provides strength which can
avoided the green body to the formation of defects such as cracking and blistering
(Heaney, 2012). The binder will be eliminated from the shaped component during
the firing process without any disruptive effect (Angelo & Subramanian, 2008).
There are ideal characteristics that binder should have followed. A good
binder that used in shaping must have low inherent viscosity at the shaping
temperature, must be strong and rigid after shaping, and should have low molecular
weight. When the binder regard to powder interaction, a binder must wet and adhere
to the powder, be chemically passive, and be stable during mixing and shaping. After
shaping process, the shaped component will be firing and the binders will be burnout.
So that, a binder must be noncorrosive and giving nontoxic products on
decomposition leave no residue on burnout, have a decomposition temperature above
and below mixing temperature. From the context of manufacturing process, a binder
that used for shaping must be readily, safe and low cost, have long shelf-life, low
water absorption and no volatile components and have high strength and stiffness
(Angelo & Subramanian, 2008).
There are investigations of producing the metal foams which contain binder.
The previous researchers study the production of micro-porous austenitic Stainless
Steels by powder injection moulding route. The material that have been used in order
to produce porous structures is 316L Stainless Steel as the main material, a multiple-
component binder system consist of Paraffin wax (PW), Polypropylene (PP),
16
Carnauba wax (CW), and Stearic Acid (SA), and spherical Poly(Methyl
Methacrylate)(PMMA) particles were used as a space holder material (Gülsoy &
German, 2008). Other investigation that produce the metallis foams was the study of
fabricating 17-4 PH Stainless Steels foam for biomedical application used
Polyvinylalcohol (PVA) as binder which added to the mixture of Stainless Steel and
Carbamide to increase the green strength of the sample (Mutlu & Oktay, 2013). Open
cell Fe-10% Al Foam was fabricated by using space holder technique by mixing
Ferum and Aluminum solution (FeAl) with Natrium Cloride (NaCl) and Polyester
resin as space holder and binder respectively in order to study the characterization of
the foams (Golabgir et al., 2014).
2.3.1 Polyethylene Glycol (PEG)
Polyethylene Glycol (PEG) is available in molecular weight from 400 to 12000 but
low molecular weights are liquids at room temperature. The most compatible
molecular weight of PEG is from 6000 to 12000 which are used in most application
at higher end. There are many type of PEG such as waxy solids that are soluble in
water, Methylene Chloride, and Acetone. PEG is clean chemical that burnout during
firing process. PEG has a low strength binder, and it is sufficient for most purpose.
Usually, PEG is added as solution or in fluid emulsion condition in order to obtain a
homogenous fluid without making a binder clotted (King, 2001). PEG is water-
soluble Polymer and frequently used as a binder, plasticizer or a lubricant. PEG
binder is about 10 times more pure compared with Polyvinyl Alcohol (PVA)
(Watchman, 2009).
There are many series of PEG members that can be categorized by its
molecular weight. The average molecular weights of 200 to 20,000 can be
categorized as the intermediate members which can be produced by the Sodium or
Potassium Hydroxide-Catalyzed batch polymerization of Ethylene Oxide onto water
or Monoor Diethylene Glycol. The fabrications of the Polymer are by stepwise
anionic addition polymerization and therefore possess a distribution of molecular
weights. Usually, the application of this type of PEG is commercial uses for products
17
in metal forming, Ceramic and Rubber –processing operations. The molecular
weights from 100,000 to 10,000,000 can be categorized as the highest members of
PEG. The fabrication of these members is by using the special anionic
polymerization catalysts that incorporate Metals such as Aluminum, Calcium, Zinc,
Iron, and coordinated ligands includes Amides, Nitriles, or Ethers. This type of PEG
is widely used because of their ability at very low concentration to reduce friction of
flowing water (Schwartz, 2002).
The application of PEG can be found in medical and biotechnical because of
the range of properties. In medical and biotechnical applications, the needs of
amphilicity behavior make PEG has widely used because of these Polymers of
Ethylene Oxide can be described as amphiphilic which can soluble both in water and
in most organic solvents. Other than that, PEG also can be found in Ceramic
applications which used as components of Ceramic slips and glazes for the
manufacture of Porcelain signs and other Vitreous coatings (Schwartz, 2002). Other
application of PEG is as a binder in manufacturing for shaping components such as
can be used in injection molding process, casting, extrusion, and powder compaction.
Figure 2.6 show the PEG that will be used in this study.
There are previous researchers that use PEG as binder such as the
investigation of fabrication of 316L Stainless Steels foam by using slurry method
used binder such PEG and Methylcellulose (CMC) (Rosip et al., 2013). There are
other researchers that used the same method of fabrication in order to investigate the
influence of composition and sintering temperature on density for pure and Titanium
Alloy foams. The Titanium slurry was prepared by mixing pure Titanium and
Titanium Alloys powder with PEG as a binder to fabricate the foams (Ahmad et al.,
2010). Rafter et al. in her study of development of SS316L foams with different
composition using compaction method use PEG as binder that mixed with SS316L
powder and crystalline Sugar as space holder (Rafter et al., 2014).
18
Figure 2.6: Polyethylene Glycol (PEG)
2.4 Space Holder
The terms Space holder play important role in order to produce metal foams. It is
important to make sure the suitable space holder is selected. The basic characteristics
of the space holder is has to be easily removable later by the thermal decomposition
either by rinsing it out or by leaching in solvents like water or alcohol. The good
criteria of space holder is its can be removed without leaving any residues and any
reaction does not occur with the metal powder, which can affect the metal powder if
the powder contains highly reactive elements like Titanium or Magnesium (Dukhan,
2013).
The size and shape of space holder also have to carefully select because of
the pores are connected to the space holder granules, elongated pores or pore
structure and tailored density gradient. When the selection process is finished, the
next process is the space holder will be mixed together with specific metal powder
and compacted into a desired shape component by conventional techniques such
axial pressing or isostatic pressing. The higher force that applied to the compact part
during compaction process due to get higher compaction pressure to make the part
have strength and the next process can be instituted. It is important to make sure the
19
strength of the compact part is sufficient enough to survive after the space holder will
be removed during sintering process (Dukhan, 2013).
There are many different space holder material that widely used includes
Polymeric material, Sodium Chloride, Crystalline Sugar Cane, Sodium Fluoride,
Carbamide, Ammonium Hydrogen Carbonate, Magnesium and Tapioca Starch
(Rafter et al., 2014). In this study, the space holder that used is Carbamide or also
known as Urea. Basically, the shape of the Carbamide is spherical and it is high
solubility in water.
Previous researcher has applied the space holder in the fabrication of metal
foams. The research to investigate the compressibility of porous Magnesium foams
which fabricated via powder metallurgy method and Carbamide (CO (NH2)2) is
choose as space holder particles (Wen et al., 2001). Other than that, other researchers
study the fabrication porous 316L Stainless Steels with two different space holder
which are Ammonium Carbonate and Ammonium Bicarbonate to compare the
properties of the metal foams by using powder metallurgy techniques (Mariotto et
al., 2011). The pure Titanium and Titanium Alloys foams were fabricated by using
the slurry method to produce the metal foams with addition the Polyethylene Glycol
as the binder and the Methylcellulose as the space holder. This aim of this
investigation was to study the characterization of the pure Titanium and Titanium
Alloys foams (Ahmad et al., 2014). The other research that involved binders
consumption is the study of powder metallurgy synthesis of Steel foams has use the
Steel powder which contain of 2.5% Ferum (Fe) and 0.2% Carbon (C) which are the
two materials that had been choose as space holder which are Magnesium Carbonate
(MgCO3) and Strontium Carbonate (SrCO3) (Park & Lakes, 2007).
2.4.1 Carbamide (Urea)
The types of space holder that frequently used are Carbamide and Ammonium
Hydrogen Carbonate. Carbamide can be removed by treatments at high temperature
either before sintering or as an initial step in the sintering heat treatment. Carbamide
is used in metal foam fabrication in order to produce porosity for certain higher
melting point metals. Carbamide also has been used as space holder for Aluminum
20
and Stainless Steel but it not being removed thermally but by water leaching. Figure
2.7 show the Carbamide particles. The particles of Carbamide have different shapes
such as rough spheres or high aspect ratio flakes. The varieties of shape for
Carbamide allow the pore shape to be controlled as this shape is preserved in the
porous material (Chang & Zhao, 2013).
Figure 2.7: Carbamide particles
There are previous researchers that used Carbamide as the space holder
material in fabrication of metallic foam. The high porosity Titanium foam was
fabricated by using Carbamide as the space holder material by applying space holder
techniques was study by the Kotan & Bor (2007). The Carbamide were dissolved in
water before mix with the Titanium powder and compacted by using conventional
pressing machine to produce Titanium foams (Kotan & Bor, 2007). The
compressibility of porous Magnesium foams which fabricated via powder metallurgy
method was studied and the Carbamide (CO (NH2)2) is choose as space holder
particles (Wen et al., 2001). The characterizing of the CR-Si-Ni-Mo Steel foams use
CR-Si-Ni-Mo Based Ancorsteel 4300 powders with the Polyvinyl Alcohol (PVA)
and Carbamide as binder and space holder material respectively was studied by
Mutlu and Oktay (2011).
21
2.5 Fabrication Techniques
There are various processes that can be classified according to the state of the
starting Metal to liquid, powdered, ionized. For liquid Metal, it can be foamed
directly by injecting gas, gas-releasing foaming agents or by producing
supersaturated Metal gas solutions. Other method that has been used such investment
casting and usage of filler materials. Metal foams also can be produced by using
Metal powder as starting materials which mix the powder with foaming agents and
compacted to a foamable precursor. The Metal slurries techniques also usually used
in order to produce Metal foams by using Polymer or powder mixtures (Banhart &
Baumeister, 1998).
2.5.1 Metal Foams Fabrication Techniques
The fabrication of Metallic foam was first start by Benjamin Sosnik in year 1948. He
produces Metallic foam by creating pores from apply Mercury vapor to molten
Aluminum and Mercury. At year 1956, the production of Metallic foam has been
done by replacing the Mercury with foaming agents generating gas by thermal
decomposition, while during year 1963 there was development of metallic foams by
a powder compacting techniques. After the sequence of history of Metallic foams
fabrication from the previous researcher, until now, many researcher have developed
Metallic foams using the techniques that avoid applying Mercury that caused the
toxicity (Chang & Zhao, 2013).
Basically, the fabrication of metal foams can be divided into two categories
which are foams made from metallic melts or in the liquid route and foams made
from solid metals or can be called as solid state route. In liquid route, it can be
described that the porosity can be derived in the form of gas bubbles either by
injecting the gas from outside or by inside by decomposed of some chemical such
like Titanium Hydride (TiH2). By contract, in solid state route, the metal powder
were used and mixed with other suitable powder or binder which can be removed
later by dissolution or decomposition such as firing process (Bhatnagar & Srivatsan,
22
2009). Figure 2.8 show the four categorizes of metal foams fabrication process
(Banhart, 2001).
Figure 2.8: Overview of the various fabrication processes of Metal foams (Banhart,
2001)
There are various fabrication method that involved in liquid sate route
categorize. The basic of the fabrication of metal foams is by direct foaming of melts.
That is impossible to directly injecting gas into the liquid in order to produce metallic
melts of foams. This is because, the high density of the liquid, the buoyancy forces
are high, and the gas bubbles that formed to the metallic melt will be influence to the
collapse of the foams. This problem can be solved by increase the viscosity of the
molten metal, modifying the surface energy of the liquid limit and etc. Investment
casting is also the method that can be categorized in liquid state route. In investment
casting, a thermo-physical shock treatment also known as reticulation is applied to
the polymeric foam. Basically, the material that used as start material is Polyurethane
foam (Dukhan, 2013).
The Syntactic foams can be produced by melt filtration which these foams
consist of a metallic matrix that attaches light weight elements. Usually, hollow
spheres are used which can be made of Glass, Ceramic, Fly Ash or Metal and
includes homogenous on it and generated closed pore structure. High pressure die
23
casting process also the method for the production of foams or sponges by comprises
the infiltration of Aluminum, Magnesium, Or Zinc melts into Polymer structures.
There are three types of fabricated metal foams by melting of foamable precursors
which are precursors produced by powder metallurgical methods, precursor
processing in the semi-solid state, and precursor fabrication from the liquid state
(Dukhan, 2013).
Nowadays, there is fabrication that no liquid metal involved, in other words
the fabrication of metal foams via solid state route. The first method to produce open
porous foams is using space holders. The suitable space holder must be select to
make sure this space holder will be easily removed later by thermal decomposition.
Next, the slurry foaming techniques is widely used in order to produce metal foams.
This method involves metal powders and a suitable carrier fluid which can be
described as solvent and polymeric binder. The syntactic foams that made via
powder metallurgy techniques are required for materials with a high melting point
like steels which melt infiltration cannot be carried (Dukhan, 2013).
In this study, the fabrication of metal foams that involved is by solid state
route. The metal foams will be produce via powder metallurgy techniques which
involved sintering and dissolution process in order to synthesize Stainless Steel metal
foams and physical properties of the foam after sintering process.
2.5.2 Fabrication Foams using Slurry Foaming Techniques
Slurry foaming technique can be described by preparing slurry which the contents is
involved, metal powders, blowing agents and some reactive additives. The next
process is to pour the slurry into mould after mixing process and left at elevated
temperatures. The additive and the blowing agent influence the slurry turns viscous
and starts to expand as gas. When the slurry can be considered as in stable condition,
the slurry need to dry completely and the sintering process will be begin. The
sintering process done for produce final product of metal foams with ideal strength.
24
Usually, slurries foaming techniques has be done in order to produce open
porous metal foams. As the example, the open porous polymer foam is dipped into a
slurry that containing a mixture of Silver and Silver Oxide powder. The foams is
coated and heated up to certain temperature, and make the Polymer inside the slurry
will be burn out and densify the metal powder particles to produced net-shaped parts
and start the sintering process and forming a rigid cellular metal structure.
There are previous researchers study the fabrication of metallic foam via
slurry method route obtains the result of density of foams down to 7% have been
achieved but there are problems with low strength and cracks in the foamed material
(Banhart, 1971). Zhou et al. in his research to fabricate Stainless Steels foam was use
slurry method to produce the metal foams with the additive of Polyurethane sponge
and high-purity Argon to the Stainless Steel powder (Zhou et al., 2008). The
morphology analysis of the Stainless Steels foams is show in Figure 2.9.
Figure 2.9: Scanning Electron Morphology (SEM) analysis of Stainless Steels
foams via Slurry Method (Zhou et al., 2008)
Ahmad et al. proposed that slurry foaming techniques in order to produce
Titanium foam with addition of PEG and CMC as binder and space holder
respectively. Polyurethane (PU) has been used as a scaffold. In the study also has
mention that slurry foaming technique can produce open celled and high porosity of
Titanium foam (Ahmad et al., 2010).
86
REFERENCES
Ahmad, S., Muhamad, N., Muchtar, a, Sahari, J., & Jamaludin, K. R. (2010).
Development and Characterization of Titanium Alloy Foams, 5(2), 244–250.
Ahmad, S., Muhamad, N., Muchtar, A., Sahari, J., Jamaludin, K. R., Ibrahim, M. H.
I., & Nor, N. H. M. (2014). Jurnal Teknologi Full paper Influence Of
Composition and Sintering Temperature on Density for Pure and Titanium
Alloy Foams, 4, 83–86.
Angelo, P. C. and Subramanian, R. Powder Metallurgy: Science, Technologies and
Applications. 2nd Ed. New Delhi. PHI Learning Private Limited. 2008.
Banhart, J. (2001). Manufacture, characterisation and application of cellular metals
and metal foams. Progress in Materials Science, 46, 559–632.
Banhart, J., & Baumeister, J. (1998). Deformation characteristics of metal foams. J.
Mater. Sci., 33, 1431.
Bhatnagar, N. and Srivatsan, T.S. Processing and Fabrication of Advanced
Materials-XVII: Vol. 1. New Delhi, India. I.K International Publishing House
Pvt. Ltd. 2009
Boudenne, A., Ibos, L., Candau, Y., & Thomas, S. (2011). Handbook of Multiphase
Polymer Systems. United States: John Wiley & Sons
Carter, C. B and Norton, M. G.Ceramic Maerials: Science and Engineering. 2nd Ed.
Iowa City. Springer Science and Business Media. 2013.
87
Chang, I. and Zhao, Yuyuan. Advances in Powder Metallurgy: Properties,
Processing and Applications. Sawston, Cambridge. Woodhead Publishing
Limited. 2013.
Chen, Y., Xu, Z., Smith, C., & Sankar, J. (2014). Recent advances on the
development of magnesium alloys for biodegradable implants. Acta
Biomaterialia, 10(11), 4561–4573.
Cobb, H. M. The History of Stainless Steel. Materials Park, Ohio. ASM
International. 2010
Davis, J. R. Handbook of Material for Medical Devices. Materials Park, Ohio: ASM
International. 2003
Davis, J. R. Alloy Digest Sourcebook: Stainless Steels. Materials Park, Ohio. ASM
International. 2000
Davis, J. R. Stainless Steels. Materials Park, Ohio. ASM International. 1994
Dukhan, N. Metal Foams: Fundamentals and Applications.Lancaster,
Pennsylvania:DEStech Publication, Inc. 2013
Gauthier, M. Structure and Properties of Open-Cell 316L Stainless Steel Foams
Produced by a Powder Metallurgy-Based Process. MetFoam’2007, 5th
International Conference on Porous Metals and Metallic Foams. 5-7 September
2007. Lancaster, Pennsylvania: DEStech Publication, Inc. 2007. ms 149-152.
Golabgir, M. H., Ebrahimi-Kahrizsangi, R., Torabi, O., & Saatchi, a. (2014).
Fabrication of Open Cell Fe-10%Al Foam by Space-Holder Technique.
Archives of Metallurgy and Materials, 59.
Groover, P. M. (2010). Fundamentals of Modern Manufacturing, Materials, Processes, and Systems. United States, America: John Wiley & Sons. Inc.
Gulsoy, H. O. and German, R. M. Production of Micro-porous Austenitic Stainless
Steel by Powder Injection Molding. Scripta Materialia. 2008. Volume 58: 295-
298
88
Heaney, D.F. Handbook of Metal Injection Molding. Sawston, Cambridge.
Woodhead Publishing Limited. 2012.
Wong, J. Y., & Bronzino, J. D. (2007). Biomaterials. Boca Rota, Florida: CRC Press.
Kalpakjian, S. and Schmid, S. R. Manufacturing Engineering and Technology.6th
Ed.New Jersey. Pearson Education, Inc. 2006
Kang, S.-J. L. (2004). Sintering: Densification, Grain Growth and Microstructure.
Massachusetts, United States: Elsevier, Butterworth-Heinemann
Kennedy, A. (2012). Porous metals and metal foams made from powders. Powder
Metallurgy, 124. Retrieved from http://www.intechopen.com/books/powder-
metallurgy/the-manufacture-of-porous-and-cellular-metals-bypowder-
\nmetallurgy-processes
King, A. G. Ceramic Technology and Processing, a Practical Working Guide.
United States, America.Noyes Publications. 2001.
Klar, E., & Samal, P. K. (2007). Powder Metallurgy Stainless Steels: Processing,
Microstructures, and Properties. Materials Park, Ohio: ASM International.
Kotan, G., & Bor, a. Ş. (2007). Production and characterization of high porosity Ti-
6Al-4V foam by space holder technique powder metallurgy. Turkish Journal of
Engineering and Environmental Sciences, 31, 149–156.
Lhuissier, P., Fallet, a., Salvo, L., & Brechet, Y. (2009). Quasistatic mechanical
behaviour of stainless steel hollow sphere foam: Macroscopic properties and
damage mechanisms followed by X-ray tomography. Materials Letters, 63(13-
14), 1113–1116.
Mariotto, S. D. F. F., Guido, V., Yao Cho, L., Soares, C. P., & Cardoso, K. R.
(2011). Porous stainless steel for biomedical applications. Materials Research,
14(2), 146–154.
Marinov. V. Manufacturing Process for Metal Products. North Dakota. Kendal Hunt
Publishing Company.2008.
89
McGuire, M. Stainless Steels for Design Engineers. Materials Park, Ohio. ASM
International. 2008.
Mutlu, I., & Oktay, E. (2013). Characterization of 17-4 PH stainless steel foam for
biomedical applications in simulated body fluid and artificial saliva
environments. Materials Science and Engineering C, 33(3), 1125–1131.
Nakajima, H. (2007). Fabrication, properties and application of porous metals with
directional pores. Progress in Materials Science, 52(7), 1091–1173.
Navarro, M., Michiardi, a, Castaño, O., & Planell, J. a. (2008). Biomaterials in
orthopaedics. Journal of the Royal Society, Interface / the Royal Society,
5(October), 1137–1158.
Park, J. and Lakes, R.S. Biomaterial: An Introduction. 3th Ed. Iowa City. Springer
Science and Business Media. 2007.
Rafat, F. (2014). Effect of different heating rate on the thermal decomposition of
urea in an open reaction vessel, 6(5), 75–78.
Rafter, M. F. M., Ahmad, S., Ibrahim, R., & Hussin, R. (2014). Development of
Stainless Steel ( SS316L ) Foam with Different Composition using Compaction
Method, 2014(Icxr120 14), 14–15.
Rao, K. V. (2002). Manufacturing Science And Technology - Manufacturing
Processess And Machine Tools. New Delhi, India: New Age International (P)
Ltd
Reardon, A. C. Metallurgy for the Non-Metallurgist. 2nd Ed. Materials Park, Ohio.
ASM International. 2011.
Rosip, N. I. M., Ahmad, S., Jamaludin, K. R., & Noor, F. M. (2013). International
Conference on Mechanical Engineering Research (ICMER2013), 1-3 July 2013
Bukit Gambang Resort City, Kuantan, Pahang, Malaysia Organized by Faculty
of Mechanical Engineering, Universiti Malaysia Pahang Paper ID: P138, (July),
1–3.
90
Ruzlan, M. S. Draman, M. K. Hashim, M.H. Megat Ismail, M.S. Saruddin, M. S. S.
Abdullah, Z. ). Study of Abrasive Wear Behaviour on Aluminium Reinforced
with 5 – 20wt. % Psc and Psbp Particles Fabricated via Conventional Powder
Metallurgy. Tesis Diploma. Politeknik Tuanku Syed Sirajuddin, Perlis. 2009.
Ryan, G., Pandit, A., & Apatsidis, D. P. (2006). Fabrication methods of porous
metals for use in orthopaedic applications. Biomaterials, 27, 2651–2670.
Shawartz, M. Encyclopedia of Materials, Parts and Finishes. 2nd Ed. Baca Raton,
Florida. CRC Press. 2002.
Shi, D. Introduction to Biomaterials. Beijing, China. Tsinghua University Press.
2006.
Stadtländer, C. (2007). Scanning electron microscopy and transmission electron
microscopy of mollicutes: challenges and opportunities.Research and
Educational Topics in Microscopy, 122–131.
Stanton, B., Zhu, L., & Atwood, C. (2009). Experiments in General Chemistry:
Featuring MeasureNet. California United States: Cengage Learning.
Tuchinskiy, L. Loutfy, R. Titanium Foams for Medical Applications. Medical Device
Materials: Proceeding of the Materials & Processes for Medical Devices
Conference. 8-10 September 2003. Materials Park, Ohio. ASM International.
2004. 377-381.
Upadhyaya, G. S. (2002). Powder Metallurgy Technology. Kanpur, India: Cambridge International Sciences Publishing.
Volicer, B. J., & Tello, S. F. (1998). d-Metal Complexes. UMass Lowel.
Watchman, J.B. Fabrication of Ceramic: Ceramic Engineering and Science
Proceeding. Volume 14, Issue 11-12. United States, America. John Wiley &
Sons. 2009.
91
Wen, C. E., Mabuchi, M., Yamada, Y., Shimojima, K., Chino, Y., & Asahina, T.
(2001). Processing of biocompatible porous Ti and Mg. Scripta Materialia, 45,
1147–1153.
YAVUZ, N. (1996). Mechanics of Powder Compaction.
Zhou, X. Y. Li, S. N. Li, J. and Liu, Y. X. Preparation of Precursor for Stainless
Steel Foam. Journal of Central South University of Technology. 2008. 15: 209-
213.